1. Field
The present disclosure relates to a fastening assembly, in particular for clamping bodies to be joined together, comprising a first element forming a first contact surface and a second element forming a second contact surface, which for producing a clamping force may be moved relative to one another in an axial direction, and comprising a device for performing a relative motion of the two contact surfaces with respect to one another, at least the second element in its extension in a direction at least substantially perpendicular to the axial direction being convertible from a compressed state to an expanded state for forming the second contact surface. The disclosure further relates to a disposable sleeve for use in such a fastening assembly.
2. General Background
Sandwich components formed from multiple interconnected layers are often used in lightweight construction, for example for use in aircraft. These layers may be composed of light metal, fiber composites, or the like. In the assembly of aircraft components, structural parts and plates must be joined to one another in a superposed manner. A liquid sealant which adhesively bonds the layers to one another is generally applied between these components made of aluminum or carbon fiber composite. These components of the sandwich structure are joined by first prepositioning the components. Temporary fastening assemblies which are inserted into holes in the sandwich structure are used to precisely position the components relative to one another, to compensate for any deformations, and by means of a defined pretensioning to press the components together and displace excess sealant, so that excess sealant can emerge as a result of this pressing.
Screw fasteners have been frequently used heretofore for clamping the layers during curing of the sealant. A screw fastener is usually provided with, for example, two spring arms which closely contact one another in the unstressed state and form an expandable prong, and which are provided on one end with a hook-like projection or border lip.
In a tightly compressed state the spring arms may be passed through a borehole in the sandwich structure until the hook-like projections emerge at the underside of the layered structure. A central mandrel is then guided between the spring arms, causing the spring arms to spread apart and the hook-like projections to engage behind the lowest ply of the layered structure. The spring arms may then be tightened against a suitable contact surface of a counterelement of the screw fastener, thereby exerting an axial clamping force on the sandwich structure. After the sealant has cured, the mandrel is removed, allowing the spring arms to once again be moved radially inward so that the hook-like projections may again pass through the borehole when the screw fastener is withdrawn from the sandwich structure. Usually a blind rivet is then inserted into the borehole to keep the sandwich structure compressed, even during operation.
A disadvantage of such screw fasteners is that the sealant may also flow into the borehole as a result of the clamping force applied by the screw fastener, and the spring arms and the mandrel for the screw fastener come into contact with the sealant. The screw fastener must therefore be thoroughly cleaned after each use, which sometimes entails high logistical effort. In addition, there is a risk that the curing sealant may prevent the spring arms from springing back after the mandrel is withdrawn, thus preventing removal of the screw fastener from the borehole.